In general, as a method of measuring a flow amount of a conductive fluid, for example, a liquid metal, an electromagnetic flowmeter or an ultrasonic flowmeter is known. Outside a duct line, the electromagnetic flowmeter includes a magnet applying a magnetic field to a conductive fluid flowing through the duct line and an electrode detecting a current generated in the conductive fluid due to a flow of the conductive fluid linked with the magnetic field, and measures an electromotive force by a magnetic field applied in a direction orthogonal to a flow direction of the conductive fluid and an electric field generated in a direction orthogonal to any of the magnetic field direction and the flow direction, thereby measuring a flow amount. The ultrasonic flowmeter includes a transmitter and a receiver for an ultrasonic wave in piping, calculates a flow rate of a conductive fluid from a time until a signal arrival using a characteristic of a propagation rate of the ultrasonic wave being related to a flow rate of a fluid, and calculates a flow amount from a known section.
In a main circulation piping system of a fast breeder reactor, since an arrangement of an electromagnetic pump and a separate flowmeter is spatially restricted, it is proposed as a method of calculating a flow amount of the electromagnetic pump to measure a terminal voltage and an input current of a winding line of the electromagnetic pump, calculate input impedance based on a ratio of the input current and the terminal voltage, and calculate a flow amount of a conductive fluid from a previously calculated relationship between the input impedance and the flow amount of the conductive fluid (Patent Document 1)